The present invention relates to a filter element for devices for cleaning the floors of swimming pools or other water-covered surfaces.
Pool cleaning devices are known, e.g., from U.S. Pat. No. 4,169,557, and comprise a small, electrically driven, track vehicle equipped with rotary brushes which clean the floor, with the water containing the dirt pried loose being drawn through a filter and, thus cleaned, being returned to the pool. A serious disadvantage of this and similar devices resides in the fact that in order to clean or replace the filter element, the device, having been removed from the water, has to be turned upside down for filter removal and return. Furthermore, there is a need for non-return valves on the bottom of the device, to prevent the high concentration of dirt returning to the pool together with the still unfiltered amount of water present in the space downstream of the filter element.
It is thus one of the objects of the present invention to provide a filter element that can be removed from and returned to the cleaning device for cleaning or replacing, without any need to turn the device upside down.
It is a further object of the invention to provide a filter element of such configuration that the solids-entraining water reaches it from above, and that the high solids concentration inside the filter can never return to the pool, obviating the need for non-return valves.
According to the invention, the above objects are achieved by providing, in combination with a swimming pool cleaning device comprising an outer shell with a detachable lid, said outer shell being open at its lower end, and an inner shell spaced apart therefrom, open at its upper end and accommodating an impeller and a clean-water exit tube, the improvement comprising a filter element having a basket-like shape including a tubular central stem configured to be seated on said exit tube, said central stem being surrounded by an annular trough constituting the active filtering portion of said element, with the outer rim of said trough being detachably affixed to said inner shell, wherein, during operation of said device, solids-entraining water drawn by said impeller enters said annular trough from above and, passing said active filtering portion, emerges therefrom as clean water to be expelled through said exit tube and returned to said pool.